Avoid releasing main thread identity on platforms that don't need to drop it, making it a platform detail.

(cherry picked from commit 92cb8246a5b67b36482ea597f23773984f53cf37)

main/main.cpp

@@ -2924,9 +2924,6 @@ Error Main::setup(const char *execpath, int argc, char *argv[], bool p_second_ph
 
 	message_queue = memnew(MessageQueue);
 
-	Thread::release_main_thread(); // If setup2() is called from another thread, that one will become main thread, so preventively release this one.
-	set_current_thread_safe_for_nodes(false);
-
 #if defined(STEAMAPI_ENABLED)
 	if (editor || project_manager) {
 		steam_tracker = memnew(SteamTracker);

platform/android/java_godot_lib_jni.cpp

@@ -50,6 +50,8 @@
 #include "core/input/input.h"
 #include "core/os/main_loop.h"
 #include "core/os/os.h"
+#include "core/os/thread.h"
+#include "core/os/thread_safe.h"
 #include "core/profiling/profiling.h"
 #include "main/main.h"
 #include "servers/camera/camera_server.h"
@@ -230,6 +232,9 @@ JNIEXPORT jboolean JNICALL Java_org_godotengine_godot_GodotLib_setup(JNIEnv *env
 		return false;
 	}
 
+	Thread::release_main_thread(); // setup2 will be called from another thread.
+	set_current_thread_safe_for_nodes(false);
+
 	TTS_Android::setup(p_godot_tts);
 
 	java_class_wrapper = memnew(JavaClassWrapper);